Ignition system



Jan. 2, 1951 B. H. SHORT ET AL IGNITION- SYSTEM Filed Feb. 16, 1949 VOLT 2 P JALM bvvs-xvmwaa BeaoKs H 51-402 Tmvo mq/e 5s E. 5110K 5y Ma 77/5/2 flrroznavs Patented Jan. 2, 1951 UNITED STATES RATENT OFFICE IGNITION SYSTEM Application February 16, 1949, Serial No. 76,722

Claims. 1

This application is a continuation in part of the copending application of Brooks I- I. Short and Charles E. Buck, Serial No. 8,768, filed February 17, 1948, now abandoned.

This invention relates to high frequency ignition apparatus having main and auxiliary condenserswhich are charged while the timer contacts are open. When the timer contacts are closed, the discharge from the auxiliary condenser renders a thyratron conductive whereupon the main condenser discharges through a circuit including the thyratron and the primary of an ignition coil.

An object of the present invention is to provide a system of this type in which cold cathode tubes are employed so that the system is ready for operation the instant the ignition switch is closed.

A further object of the present invention is to increase the .duration of the are at the spark plug so that the fuel mixture will receive heat sufiicient to start combustion without requiring a long are for this purpose. By increasing the duration of the arc, the arc can be made shorter and less potential is required to start the arc.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a wiring diagram of an ignition system embodying the present invention.

Figs. 2, 3 and 4 are charts illustrating its operation.

Referring to Fig. 1, a generator G driven by the automobile engine supplies current through a cut out relay to a storage battery IE3. This relay closes when generator voltage is above battery voltage and opens when the former voltage is below the latter. During cranking current for operating the ignition apparatus is supplied by the battery Ill and during running with the cut out relay closed generator G supplies current for the ignition apparatus. A voltage regulator not shown limits generator voltage to a certain value. These current sources are connected by a switch I! with a power supply comprising a transformer II, a vibrator 2| and rectifiers 3| connected in a voltage doubler circuit. Transformer I I includes two primary windings divided into sections I2 and i4, i3 and I 5 and a secondary winding IS. The center taps of the primary windings are connected with battery I0, through an ignition switch 11, a concentric condenser I8 and an. impedance choke I!) connected to a grounded condenser 26. The elements l8, l5 and 23 provide for elimination of interference with adjacent radio apparatus.

The vibrator 2% comprises a core 22 surrounded by coil 23, an armature 24 carried by reed 25 which is grounded and carries contacts 26 and 2? engageable respectively with side contacts 28 connected with the ends of primary sections i3 and i5 and with side contacts 29 connected with the ends of primary sections .12 and M. By dividing the primary, the current carried by the contacts of the vibrator is maintained within practical limits.

The ends of the secondary it are connected with wires 32 and 33 between which a condenser 36 is connected. Wire 32 is connected with the cathode of upper tube 34 and with the plate of lower tube 3!. Wire is connected with re.- sistances 35 connected with elements 35a which start electron emission in tubes 3!. Wire 33 is connected between condensers 36 and 37, the latter being grounded and the former being connected with a wire 38 leading from the cathode of one of the tubes 31 tothe power Supply terminal 39 which is maintained at a potential of 1500 volts, for example, when the generator or the battery apply full voltage. If the battery is not fully charged but has enough charge to crank the engine and supply current for the ignition system, the potential at terminal 38 may be as low as 800 volts.

Wire 39 connects positive terminal 3% with resistance M which controls charge rate of main condenser 4:! connected therewith, with resistance 6i] which controls charge rate of spark prolonging condenser ti connected therewith, and with a voltage absorbing resistance 42 connected with a terminal 56. Resistance G! is connected with the plate of a thyratrcn 43. The main condenser M; is connected with a primary winding 45 of a high frequency ignition coil at whose secondary cl is connected with condenser E! and with engine spark plugs through a suitable distributor, not shown. One of the spark plugs is indicated at 48.

Resistance s2 is connected with a wire connected through a resistance 5! and a voltage limiting device or regulator 52 with a wire 53. Regulator 52 limits the potential between wires 56 and 53 to a certain value, for example, 750 volts. Wire 58 is connected with auxiliary condenser 59 through a charge rate controlling resistance 54- connected with contact 55 of ignition timer 5?. Contact 55 is engageable with timer contact 56 connected with the grid 43a of the thyratron 63. Resistance 58 connects the grid of thyratron 43 with the thyratron cathode through wire 53 connected with the negative or ground terminal of the power supply with which terminals of 52, 55 and ed are connected.

satisiactory operation has been obtained by using elements having the ioilowing model designations or electrical characteristics:

Transformer primaries--each 22 turns of #17 wire;

Transiormer secondary I6-3000 turns of wire;

Condenser E i-.003 mid;

(3nd resistances 3c-lU megohms;

Rectifier tuoes 3l-model CK 1013;

Condensers 3t and 3'i1.3 mid;

Resistance dib0,UUO ohms, cu watts;

Resistance d222o,000 ohms, 2 watts;

Resistance 5 l 3UU,UUO ohms, 1 watt;

Resistance 5 ll megohm, 1 watt;

Resistance 582'Z,U00 ohms, 1 watt;

Resistance 6c25,000 ohms;

Condenser l i.02 mfd.

Condenser 59.003 mfd.;

Condenser iii-08 mid;

Tube 3-model 2M 324 cold cathode thyratron;

Voltage regulator 52-twelve 60-volt neon bulbs in series.

Condenser 3 is a buffer condenser which ab- I sorbs transient voltages when the vibrator contacts open.

The high frequency ignition coil 46 is constructed in the manner disclosed in the patent of Short and Tynan, No. 2,l63,l23, granted March 1, 1949.

Tubes 3 l known as cold cathode tubes, because they do not have heated cathode filaments, become conducting by an electrostatic field created by the application of relatively high voltage from the transformer secondary. The conduction by these tubes is started by elements em in close proximity to the cathode. Each element 3m sets up an electrostatic field which causes electrons to be emitted and causes the tubes 31 to be conduct- When wire 33 is positive, condenser 31 is charged through the circuit: wire 33, condenser 3?, ground and upper tube 3!. When wire 32 is positive, condenser 36 is charged through the circuit; wire 32, lower tube 3!, condenser 36, wire 33. This circuit arrangement causes the potential of terminal 353 to be twice the potential of each condenser. Hence the condensers 36 and 37 provide a voltage doubler.

Tube :33 requires positive potential on its grid ita in order to become conducting. Having once become conducting, it will continue to conduct so long as the plate voltage is above the ionization voltage, for example 100 volts. Resistance M lim'ts the rate of charging condenser dd. When condenser dd is fully charged, its potential becomes the potential of terminal 39. When tube 53 becomes conducting due to discharge of conwhen engine speed is low. the generator supplies current to the power sup- 4 obtained when the voltage of a partly charged battery is low but yet sufiicient to en'ect operation or the engine cranliing motor and is low volts, for example, when the battery is iully charged when operating the cranising motor or when current is supplied by the generator Ior ignition and battery charging. In order to provide for adequate charging of condenser 5:: when terminal t9 potential is ecu volts and not sub ect it to excessive voltage when terminal 39 potential is higher than 380 volts, the voltage regulator or voltage limiting device 52 is provided. Device comprises twelve neon tubes in series which do not pass current 11" the applied voltage is below I50 volts. The difference in potential between voltage of terminal as and 750 volts is absorbed in IR drop in resistance 42. So long as the potential of terminal 39 exceeds 756 volts, voltage regulator e2 takes 750 and resistance 42 absorbs the excess. Therefore, the potential or" condenser be, when i'ully charged, cannot exceed 750 Volts.

Resistance 52, which with resistance 42 forms a voltage divider, serves as a bleeder resistance which icy-passes current from the voltage regulator and thus lightens the load thereon.

Resistance tit limits the rate of voltage increase of condenser 5%, thereby permitting the timer contacts to be well separated before the condenser can become fully charged to a potential required for triggering. However, because regulator 52 is not conducting until the potential of the terminal at reaches 750 volts, no current is diverted by regulator 52 before it becomes conducting. Hence the current flow to the condenser 59 will be greater and it will accumulate its energy in less time than it would if the regulator 52 were conducting at all times. In Fig. 2, horizontal distances denote time and vertical distances denote voltage. Under a condition of low battery voltage when potential of terminal 39 is 800 volts, for example, line DEC represents voltage of condenser 59 and line ABC represents voltage of terminal 55. At the instant represented by 0 when charging of condenser 5d starts, voltage of terminal 5i] is 250 volts, the IR drop in resistance 32 being 550 Volts when voltage of terminal 39 is 800 volts. 250 volts less IR drop in resistance til is applied to condenser 59 at instant zero. Voltage of condenser 59 rises as represented by line D E and the current passing to it decreases. As current taken by condenser 59 decreases, the

IR drop in resistance 52 decreases and potential of terminal 53 rises as represented by line AB. When time tihas elapsed voltage of terminal 55 has reached 750 volts and can go no higher because regulator 52 then starts to conduct and limits the potential of terminal 50 to 750 volts.

Thereafter the rate of voltage rise of condenser 59 takes place less rapidly as represented by line E-C while potential of terminal 58 remains at 750 volts as represented by line 3-0. Condenser 59 is charged to 750 volts in time t2.

If the potential of terminal 33 were higher than 800, voltage at A would be higher and times t and t2 would be less. If the potential of terminal 39 is 1500 volts, for example, the system operates so that the potential at terminal 50 is less than 750 volts at 0 time or the instant when the charging of condenser 59 starts. This is desirable since the regulator 52 consumes energy from the power supply and should not be operative any longer than necessary. Time 152 is sufficient for adequate ignition during cranking During running when sistance 5| which takes some of the load off the regulator 52. The value of this current passed by resistance 42 is that which causes the IR drop therein to equal potential of terminal 39 minus 750 volts.

Resistance 58 ties the grid 43a to the cathode of tube 43 so that its potential equals cathode potential when the timer contacts open. The value of resistance 58 is between a too high value by which control of the grid will be lost and a too low value which would result in the diversion of too much energy from the condenser 59 when discharging.

While the timer contacts 55, 56 are open, condenser 59 is being charged. When the contacts close, condenser 59 discharges to the grid 43a, and tube 43' becomes conducting so that condenser 44 discharges through primary winding 45 of ignition coil 46. Voltage in secondary winding 47 rises to such value that an arc is established at the gap 48 of the spark plug and a discharge circuit for condenser BI is established. The arc having been established by attainment of acquired secondary voltage, the duration of the arc is prolonged by discharge of condenser Bl. By prolonging the duration of the arc, the'surrounding fuel mixture will receive suficient heat to start combustion. Therefore, ignition can be efiected with a relatively short spark gap. Fig. 4 shows that the secondary voltage V2 required to start the arc may be, for example, 18 KV. Time is of Fig. 4 represents the time of the decline of voltage peak P2 plus the time which elapses before the voltage of condenser 6| falls below the value required to maintain the arc. Line 65d represents the discharge of condenser M to maintain the are. If no means are provided to maintain the are after the peak voltage has dropped below the value required to maintain the arc, the duration of the arc is much shorter. Therefore the arc must be longer in order that the surrounding fuel mixture will be heated sufficiently to start combustion. Since the arc must be longer, the peak voltage must be higher. For example, the apparatus with condenser 6| will provide ignition at 18 kv., secondary peak voltage, for a particular engine. Without condenser 6i, satisfactory ignition would not be provided for that engine unless the spark gap is widened to such extent that 38 kv. is required to start the are as indicated at P1 in Fig. 3. The duration of the arc is represented by 151 in Fig. 3 which is considerably smaller than t2 in Fig. 4. To obtain secondary voltage high enough to start the arc, the condenser 44 must be larger and the coil 46 must have a higher transformation ratio. A larger and more expensive tube 43 would be required to handle the larger amount of current discharged by condenser 44.

The present system is operative the instant the ignition switch I1 closes since cold cathode rectifier tubes 3| and a cold cathode thyratron tube 43 are used. These tubes require high voltage for their operation without cathode heaters. The

power supply which includes the rectifier tubespower supply is capable of operation when the potential of terminal 39 is low due to low state of battery charge as well as when the potential of terminal 39 is high; The system provides for adequate charging" of the main condenser" 44 in the range or potential variation of terminal 39 and for adequate chargingof condenser 59 when the potential of terminal 39 is at the low limit. To prevent application of excessive voltage to condenser 59, the system includes a voltage limiting device (regulator 52) and a voltage absorbing device (resistance 42). currentwhich condenser 59 takes whenits charg ing begins, resistance 42 absorbs such amount of voltage, that the regulator cannot operate initially and is not normally an energy consuming device. As the charging of condenser 59 increases, its voltage increases and the current re ceived by it decreases and thevoltage consumed by resistance 42 decreases and the voltage impressed on the regulator 52 increases. The regulator 52 operates to limit the voltage-impressed on the condenser 59 regardless ofvariation of potential of terminal 39 in the operating range. Therefore the voltage applied to grid 43 when condenser 59 discharges never becomes excessive and tube 43 is not damaged although its plate voltage may vary with voltage of terminal 39.

By rendering regulator 52 operative only when needed, electrical energ is conserved and a less expensive power pack can be'used. Furthermore, electrical energy is conserved through the use of the are maintaining condenser El since satisfactory ignition is provided when the spark plug gaps are relatively short thereby requiring less energy to start the arc.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form,

it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An ignition system for automotive vehicles comprising a storage battery, a power supply having an output terminal and receiving current from the battery and furnishing relatively high voltage direct current to the output terminal, an induction coil, a main condenser connected with the output terminal and with the primary winding of the induction coil, a discharge circuit for the main condenser including a cold cathode thyratron which conducts when a certain positive potential is impressed on its grid, a circuit for periodically supplying the required positive potential to the grid of the thyratron and including an auxiliary condenser and contacts of the engine operated ignition timer which, when closed, cause the auxiliary condenser to discharge through the thyratron grid, and means connected with the output terminal and operating independently of the state of battery charge, within certain limits, and consequent change in power supply output voltage for controlling application upon the auxiliary condenser to charge it of a voltage which is limited to a predetermined value, said means comprising a device which passes current only when voltage of said predetermined value is applied to it and a resistance which absorbs the potential in excess of By virtue of the 7 said value, said device and the auxiliary condenser being connected in parallel and together in series with the resistance. 7

2, Thesystem according to claim 1 in which the device is a bank of a plurality'of neon tubes in series.

3, The system according to claim 1 in which the device is a bank of a plurality of neon tubes in series and in which there is a bleeder resistance in parallel with the bank of neon tubes to lighten the loa d thereon, v W 7 4. An ignition system comprising a current source, an ignition coil having primary and secondary windings, a spark gap connected with the secondary winding, a main condenser charged by the source, a main condenser discharge circuit including the primary winding and a thyratron, an auxiliary condenser charged by the source, an auxiliary condenser discharge circuit including ignition timer contacts and the grid of the thyratron, the closing of the contacts causing the thyratron to establish the main condenser discharge circuit whereby secondary voltage increases to a value to produce an are at the spark gap and a third condenser charged by the source and connected in series with the secondary Winding and spark gap and discharging through the circuit established by the arc and operating to maintain the arc until the discharge voltage of said third condenser falls below arc-maintaining voltage.

5. An ignition system for use on an automotive vehicle having a storage battery and battery charging generator operated by the vehicle propeller engine, a power supply which receives relatively low voltage direct current from the batter or from the generator when it charges the battery and which produces relatively high voltage at its terminals, one of which is positive, the other or negative terminal being grounded, an ignition coil having a primary and secondary winding, a spark gap and an arc-prolonging condenser in series with the secondary windings, a

charge-rate controlling resistance connecting the arc-prolonging condenser with the positive terminal of the power supply, a main condenser and a second charge-rate controlling resistance connected in series with the primary winding and said positive terminal, a main condenser discharge circuit including the primary windings and a code cathode thyratron, an auxiliary condenser, means connected with said power supply and au ili onden e la d op ratin independently of the state of battery charge, Within certain limits, and consequent change in power supply output voltage to control the application upon the auxiliary condenser to charge it of a voltage which is limited to a predetermined value, said means comprising a device which passes current only when voltage of said predetermined value is applied to it and a resistance which absorbs the potential in excess of said value, said device and the auxiliary condenser being connected in parallel and together in series with the resistance, there being a charge-rate controlling resistance connecting a terminal of the auxiliary condenser with the device and the potential-absorbing resistance, and an auxiliary condenser discharge circuit which includes engine controlled timer contacts, when closed, the grid and the cathode of the thyratron.

BROOKS H. SHORT. CHARLES E. BUCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,745,830 Bethenod Feb. 4, 1930 2,409,202 Francis Oct. 15, 1946 2,463,123 Short et a1 Mar. 1, 1949 

